构建详情视图

Leanback androidx 库提供的媒体浏览界面类包含用于显示媒体项目相关附加信息(如说明或评价)的类。它们还包含用于对相应商品执行操作的类,例如购买该商品或播放其内容。

本指南介绍如何为媒体项目详情创建 Presenter 类,以及如何扩展 DetailsSupportFragment 类以在用户选择媒体项目时为项目实现详情视图。

注意:此处显示的实现示例使用一个额外的 activity 来包含 DetailsSupportFragment。不过,使用 fragment 事务可以在同一个 activity 中将 BrowseSupportFragment 替换为 DetailsSupportFragment,从而避免创建第二个 activity。如需详细了解如何使用 fragment 事务,请参阅创建 fragment

构建详情 Presenter

在 Leanback 库提供的媒体浏览框架中,您可以使用 Presenter 对象来控制数据(包括媒体项目详情)在屏幕上的显示。为此,该框架提供了 AbstractDetailsDescriptionPresenter 类,该类几乎是对媒体项目详情 Presenter 的完整实现。您只需实现 onBindDescription() 方法,将视图字段绑定到您的数据对象,如以下代码示例所示:

Kotlin

class DetailsDescriptionPresenter : AbstractDetailsDescriptionPresenter() {

    override fun onBindDescription(viewHolder: AbstractDetailsDescriptionPresenter.ViewHolder, itemData: Any) {
        val details = itemData as MyMediaItemDetails
        // In a production app, the itemData object contains the information
        // needed to display details for the media item:
        // viewHolder.title.text = details.shortTitle

        // Here we provide static data for testing purposes:
        viewHolder.apply {
            title.text = itemData.toString()
            subtitle.text = "2014   Drama   TV-14"
            body.text = ("Lorem ipsum dolor sit amet, consectetur "
                    + "adipisicing elit, sed do eiusmod tempor incididunt ut labore "
                    + " et dolore magna aliqua. Ut enim ad minim veniam, quis "
                    + "nostrud exercitation ullamco laboris nisi ut aliquip ex ea "
                    + "commodo consequat.")
        }
    }
}

Java

public class DetailsDescriptionPresenter
        extends AbstractDetailsDescriptionPresenter {

    @Override
    protected void onBindDescription(ViewHolder viewHolder, Object itemData) {
        MyMediaItemDetails details = (MyMediaItemDetails) itemData;
        // In a production app, the itemData object contains the information
        // needed to display details for the media item:
        // viewHolder.getTitle().setText(details.getShortTitle());

        // Here we provide static data for testing purposes:
        viewHolder.getTitle().setText(itemData.toString());
        viewHolder.getSubtitle().setText("2014   Drama   TV-14");
        viewHolder.getBody().setText("Lorem ipsum dolor sit amet, consectetur "
                + "adipisicing elit, sed do eiusmod tempor incididunt ut labore "
                + " et dolore magna aliqua. Ut enim ad minim veniam, quis "
                + "nostrud exercitation ullamco laboris nisi ut aliquip ex ea "
                + "commodo consequat.");
    }
}

扩展详情 Fragment

使用 DetailsSupportFragment 类显示您的媒体项目详情时,请扩展该类以提供其他内容,例如媒体项的预览图片和相关操作。您还可以提供其他内容,例如相关媒体项的列表。

以下示例代码演示了如何使用上一部分中显示的 Presenter 类为正在查看的媒体项添加预览图片和相关操作。此示例还展示了如何添加相关媒体项行,该行显示在详情列表下方。

Kotlin

private const val TAG = "MediaItemDetailsFragment"

class MediaItemDetailsFragment : DetailsSupportFragment() {
    private lateinit var rowsAdapter: ArrayObjectAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        Log.i(TAG, "onCreate")
        super.onCreate(savedInstanceState)

        buildDetails()
    }

    private fun buildDetails() {
        val selector = ClassPresenterSelector().apply {
            // Attach your media item details presenter to the row presenter:
            FullWidthDetailsOverviewRowPresenter(DetailsDescriptionPresenter()).also {
                addClassPresenter(DetailsOverviewRow::class.java, it)
            }
            addClassPresenter(ListRow::class.java, ListRowPresenter())
        }
        rowsAdapter = ArrayObjectAdapter(selector)

        val res = activity.resources
        val detailsOverview = DetailsOverviewRow("Media Item Details").apply {

            // Add images and action buttons to the details view
            imageDrawable = res.getDrawable(R.drawable.jelly_beans)
            addAction(Action(1, "Buy $9.99"))
            addAction(Action(2, "Rent $2.99"))
        }
        rowsAdapter.add(detailsOverview)

        // Add a related items row
        val listRowAdapter = ArrayObjectAdapter(StringPresenter()).apply {
            add("Media Item 1")
            add("Media Item 2")
            add("Media Item 3")
        }
        val header = HeaderItem(0, "Related Items")
        rowsAdapter.add(ListRow(header, listRowAdapter))

        adapter = rowsAdapter
    }
}

Java

public class MediaItemDetailsFragment extends DetailsSupportFragment {
    private static final String TAG = "MediaItemDetailsFragment";
    private ArrayObjectAdapter rowsAdapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.i(TAG, "onCreate");
        super.onCreate(savedInstanceState);

        buildDetails();
    }

    private void buildDetails() {
        ClassPresenterSelector selector = new ClassPresenterSelector();
        // Attach your media item details presenter to the row presenter:
        FullWidthDetailsOverviewRowPresenter rowPresenter =
            new FullWidthDetailsOverviewRowPresenter(
                new DetailsDescriptionPresenter());

        selector.addClassPresenter(DetailsOverviewRow.class, rowPresenter);
        selector.addClassPresenter(ListRow.class,
                new ListRowPresenter());
        rowsAdapter = new ArrayObjectAdapter(selector);

        Resources res = getActivity().getResources();
        DetailsOverviewRow detailsOverview = new DetailsOverviewRow(
                "Media Item Details");

        // Add images and action buttons to the details view
        detailsOverview.setImageDrawable(res.getDrawable(R.drawable.jelly_beans));
        detailsOverview.addAction(new Action(1, "Buy $9.99"));
        detailsOverview.addAction(new Action(2, "Rent $2.99"));
        rowsAdapter.add(detailsOverview);

        // Add a related items row
        ArrayObjectAdapter listRowAdapter = new ArrayObjectAdapter(
                new StringPresenter());
        listRowAdapter.add("Media Item 1");
        listRowAdapter.add("Media Item 2");
        listRowAdapter.add("Media Item 3");
        HeaderItem header = new HeaderItem(0, "Related Items", null);
        rowsAdapter.add(new ListRow(header, listRowAdapter));

        setAdapter(rowsAdapter);
    }
}

创建详情 Activity

DetailsSupportFragment 这样的 Fragment 必须包含在要用于显示的 Activity 中。通过为详情视图创建 activity(与浏览 activity 分开),您可以使用 Intent 调用详情视图。本部分介绍了如何构建一个 activity 来包含对媒体项详情视图的实现。

通过构建一个引用 DetailsSupportFragment 实现的布局,来创建详情 activity:

<!-- file: res/layout/details.xml -->

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    android:name="com.example.android.mediabrowser.MediaItemDetailsFragment"
    android:id="@+id/details_fragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
/>

接下来,创建一个使用上一个代码示例中所示的布局的 activity 类:

Kotlin

class DetailsActivity : FragmentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.details)
    }
}

Java

public class DetailsActivity extends FragmentActivity
{
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.details);
    }
}

最后,将这个新 activity 添加到清单中。请务必应用 Leanback 主题,以确保界面与媒体浏览 Activity 保持一致。

<application>
  ...
  <activity android:name=".DetailsActivity"
    android:exported="true"
    android:theme="@style/Theme.Leanback"/>

</application>

为点击的项目定义监听器

实现 DetailsSupportFragment 后,请将您的主媒体浏览视图修改为在用户点击媒体项时切换到详情视图。如需启用此行为,请将 OnItemViewClickedListener 对象添加到 BrowseSupportFragment,以便触发启动商品详情 activity 的 intent。

以下示例展示了如何实现一个监听器,以在用户点击主媒体浏览 Activity 中的某个媒体项时启动详情视图:

Kotlin

class BrowseMediaActivity : FragmentActivity() {
    ...
    override fun onCreate(savedInstanceState: Bundle?) {
        ...
        // Create the media item rows
        buildRowsAdapter()

        // Add a listener for selected items
        browseFragment.onItemViewClickedListener = OnItemViewClickedListener { _, item, _, _ ->
            println("Media Item clicked: ${item}")
            val intent = Intent(this@BrowseMediaActivity, DetailsActivity::class.java).apply {
                // Pass the item information
                extras.putLong("id", item.getId())
            }
            startActivity(intent)
        }
    }
}

Java

public class BrowseMediaActivity extends FragmentActivity {
    ...
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        // Create the media item rows
        buildRowsAdapter();

        // Add a listener for selected items
        browseFragment.OnItemViewClickedListener(
            new OnItemViewClickedListener() {
                @Override
                public void onItemClicked(Object item, Row row) {
                    System.out.println("Media Item clicked: " + item.toString());
                    Intent intent = new Intent(BrowseMediaActivity.this,
                            DetailsActivity.class);
                    // Pass the item information
                    intent.getExtras().putLong("id", item.getId());
                    startActivity(intent);
                }
            });
    }
}